According to them, the edits to adjust the overt graphics are only minor and were approved by developer AquaPlus.

Here’s Atlus’s full statement on the censoring:

Dungeon Travelers 2: The Royal Library & the Monster Seal presented some challenges during the localization process — specifically, adapting some of the fan service content to western sensibilities. Localization by nature requires some changes to be made for content to be understood en masse, which is why Atlus worked closely with developer AquaPlus to preserve the game’s themes and content to its fullest.

In order to comply with restrictions set forth by rating boards, Atlus made concessions on just four in-game images. On these images, some minor edits were made (and approved by the developer) to adjust the overt graphics to within acceptable ranges for the game’s M-rating.

Atlus is committed to being one of the leading publishers of niche JRPGs, and are very aware of what impact censorship can have on import titles; we are confident that the changes we made to the images in Dungeon Travelers 2 were the least invasive possible to still be eligible for a release in the west.

Thematically, the game remains as true as possible to the original Japanese version, including the preservation of the original Japanese audio.